This paper presents and discusses the results of an attempt that was made to determine the Type X, 12.7 mm and 15.9-mm-thick, gypsum board fall-off in fire resistance tests of different orientations (horizontal and vertical assemblies) for 83 and 41 full-scale floor and wall test assemblies, respectively. These tests were conducted at the National Research Council of Canada in accordance with the CAN/ULC–S101 standard, which is similar in fire exposure to the ASTM E119 fire resistance standard for updating the fire resistance ratings in the listed wall and floor assemblies in Part 9, Appendix A, of the National Building Codes of Canada. The results of tests were further analyzed to investigate the gypsum board fall-off for wall and floor assemblies. Four different approaches were investigated using the floor assemblies' test results to identify board fall-off criterion. The proposed temperature criterion selected is based on the sudden temperature rise on the back side of the fire exposed gypsum board due to the board fall-off. The same criterion was also used in predicting the gypsum board fall-off in wall assemblies. A comparison of the gypsum board fall-off based on test observations and temperature measurements and temperature criteria for gypsum board fall-off for both vertical and horizontal applications are presented and discussed.